Preparation Of Carboxymethyl Cellulose Composite Gel Microspheres And Study On Their Slow-release And Catalytic Properties

Carboxymethyl cellulose(CMC)is the most widely used anionic cellulose derivative in medicine,photocatalytic degradation,tissue engineering,petroleum,food and energy storage,with the advantages of extensive resources,excellent water solubility,surface modification,biodegradability and biocompatibility.Hydroxyl and carboxyl groups fill the surface of CMC,which are easy to be functionalized and modified.In this work,CMC composite microspheres with different functions were prepared from CMC by reverse-phase suspension polymerization and ion crosslinking,aiming to reveal the synthesis mechanism and expand the potential application of CMC composite microspheres in photocatalysis and sustained release.(1)CMC hydrogel(CDMG)microspheres with controllable morphology were prepared by inverse suspension polymerization and microfluidic technology.The maximum swelling ratio of CDMG microspheres in deionized water and normal saline was 8725 g g-1 and 767 g g1,respectively.CMC aerogel microspheres were prepared by freezing CDMG microspheres at different freezing temperatures.The internal microscopic morphology of CDMG aerogel can be adjusted from continuous open 3D porous network structure to 2D sheet structure and finally to nanofiber structure by adjusting the material ratio,swelling degree and freezing rate of CDMG microspheres.It provides basic theoretical support for the controllable preparation and the internal morphology regulation of CDMG microspheres.(2)A novel CMC slow-release fertilizer(CDFG)microspheres were successfully prepared by reverse-phase suspension polymerization and simple adsorption,using CMC and ?cyclodextrin(?-CD)as raw materials.It presented rich 3D network structure,which is beneficial to fertilizer adsorption and sustained release.In the solution of pH(2?12)and different types of salt solution,CDFG microspheres showed good acid and alkali resistance and salt resistance.The fertilizer absorption rate of CDFG microspheres reached 3342.84 g g-1 in 5 g L-1 urea solution.In the soil culture experiment,urea in the CDFG microspheres is completely released within 7 days,while the pure urea is completely released within 1 day.The release mechanism of urea in CDFG microspheres showed to the non-Fick diffusion.Degradation rate of CDFG hydrogel microspheres by Aspergillus Niger reached 98.2%in three days.In this work,CDFG microspheres are easy to obtain with the excellent biodegradability,which has broad application prospects in the field of agriculture and forestry.(3)CMC drug loading hydrogel(DOX@CDGO)microspheres with pH response were prepared using CMC and graphene oxide(GO)as raw materials and doxorubicin hydrochloride(DOX)as slow-release drug model.When the amount of GO was 3 wt%,CDGO microspheres with uniform pore size were obtained.In deionized water,the maximum swelling ratio of CDGO3 was 5617.94 g g-1.The cumulative release of DOX in DOX@CDGO3 composite hydrogel microspheres was pH-dependent,and the cumulative DOX release rate reached 97.01%in acidic medium(pH=5.8).In the cytotoxicity experiment,when CDGO3 and HeLa cells were co-cultured for 72 h,the cell survival rate was still greater than 98%,indicating that CDGO3 has good biocompatibility and DOX cytotoxicity was reduced.Nude mice were used as animal models.In vivo safety evaluation showed DOX@CDGO3 is beneficial to anti-tumor,no obvious toxic on the main organs,and inhibitory and destructive effects on tumor growth.This work provides basic theory support for the construction of sustained release system of CMC drug loaded hydrogel microspheres.(4)Graphite carbon nitride/CMC aerogel(GHAs)composite microspheres were successfully prepared by high temperature calcination and reverse suspension polymerization using CMC and urea.GHAs composite microspheres presented rich 3D network structure and provides sufficient active sites for photocatalytic reaction.The photocatalytic activity of GHAs composite microspheres was evaluated using rhodamine B(Rh B)as photocatalytic degradation model.The photo-degradation rate of Rh B by GHAs composite microspheres was 97.99%after 90 min under visible-light irradiation.The photocatalytic reaction rate constant was 4.25 times higher than that of carbon nitride.Mechanistic studies reveal that the superoxide radicals(·O2-)are the main active groups in the photodegradation process.In five cycling experiments,GHAs composite microspheres showed good photocatalytic stability.GHAs composite microspheres are easy to separate and have perfect application value in practical environmental governance.(5)Strontium-bismuth titanate/graphite carbon nitride/CMC aerogel(SBNCSNx)composite microspheres with photocatalytic properties were successfully prepared by hightemperature calcination and ion crosslinking.CMC and sodium alginate are used as raw materials,and graphite carbon nitride and strontium-bismuth titanate are used as photocatalytic active agents.The piezo-photo synergistic catalytic activity of SBNCSNx composite microspheres was tested by using Rh B as degradation model.The degradation rate of Rh B by SBNCSNx composite microspheres was 99.97%after 60 min under piezo-photo synergistic catalytic.In five cycling experiments,the degradation removal rate of Rh B was only reduced 8.09%,which showed good piezo-photo synergistic catalytic stability.Active species trapping experiments confirmed that ·O2-is the main active species involved in piezo-photo synergistic degradation of organic pollutants.·O2-generation rate was 38.26 ?mol h-1.In summary,SBNCSNx composite microspheres had good piezo-photo synergistic catalytic performance and has a good application prospect in the field of environmental wastewater purification.